Underwater sound system



March 19,1957 Rm UNDERWATER SOUND SYSTEM Filed LE; 1949 45 4 INVENTOR.STANLEY R RICH BY &

HIS AT OR Y UNDERWATER scorn) SYSTEM Stanley R. Rich, Newton (Ienter,Mass, assignor to Raythenn Manufacturing Company, a corporation ofDelaware Application March 19, 1948, Serial No. 14,017

15 Claims. (Cl. 340-6) This invention relates to an electronic scanningsystem particularly applicable for use in echo ranging and directionfinding in which scanning may be accomplished for a complete 360 azimuthcircle or for sectors of less angular magnitude rapidly and without theuse of rotating wave transducers.

The present scanning system involves. the use of a plurality of fixedwave transducers or the like which, in a 360 scanning system, arearranged uniformly about a circle or other symmetrical figure in theplane in which scanning or transmission is to be accomplished incooperation with a plurality of electrical delay lines in an arrangementwhich, as will appear herein, is aptly termed a lens network, and ischaracterized by low energy loss and correspondingly high etficiency.Each transducer is permanently connected to one end of an electricaldelay line upon which the signals are impressed and the delay lines areeach preferably terminated in its characteristic impedance. inaccordance with the further development of the present system, there isalso coupled by transformer action to the delay line inductors aplurality of groups of coils in the nature of secondary windings ofwhich the coils in each group are connected in series, all the groupsterminating in a selector switch mechanism by means of which the groupsare selectively connected in turn to a power source or an output circuitfor selecting the desired directivity of the array of transducers as awhole.

The invention operates in accordance with the maximum intensityprinciple whereby, for example, the impulses received in each transducerare compensated to bring them into approximately the same phase for adesired directivity whereby a maximum intensity efiect is obtained andobserved in one direction and a minimum at all others. The indication,for received signals, may be produced visually by means of a cathode rayoscilloscope with a rotating beam upon which the indication is impressedto produce the desired eifect. The beam may be suppressed until a signalis received to cause the beam to produce a spot on the face of theoscilloscope tube, or electrostatic deviation plates or electromagneticcoils may be used for producing a deflection of the beam trace.

As a selector switch mechanism the present invention preferably employsan electronic commutator switch tube such as that which is described inthe copending application Serial No. 655,447, filed March 19, 1946, nowPatent No. 2,684,449.

The present invention will be more fully described in the specificationset forth below, taken in connection with the drawing illustrating anembodiment of the same, showing a schematic diagram of a system inaccordance therewith.

In the figure the wire is shown only for a portion of the whole numberof transducers, it being understood that the same scheme is followedthrough for. the entire array. This method of illustration has beenemployedfor the purpose of simplicity and to maintain ata minimum, thenumber of drawings, more of which, it is believed, would it StatesPatent not materially add to the understanding of the invention.

The transducers 1 to 21, inclusive, may each be a sonic or supersonicreceiver, for example, for underwater use, in which case they arepositioned in the external water or in a sea chest within a vessel, butaccessible acoustically to the surrounding medium. The transducersmaintain their respective spacings as indicated in the drawing; that is,they are uniformly spaced apart about a circumference in a plane. Sinceonly a portion of the phasing system is shown, transducers 11 to 21,inclusive, are shown in dotted lines. All of the transducers have,preferably, a common ground 22 for one terminal connection while theother terminal of each unit is connected via one of wires 23 to 32,inclusive, to an end of one of the delay lines 33 to 42, respectively.The signals received by the transducers and transmitted to therespective delay lines travel down to the ends of the lines, which areeach terminated with a. proper impedance 43 by means of which noreflections are produced. Each delay line comprises a well-knownarrangement of series connected inductances. Selected ones of theinductances of each line, as, for instance, 44, 45, 46, 47 and 48 ofline 33, are each coupled, transformer fashion, and preferably tightly,to two secondary windings 44' and 44", 45 and 45", etc., by means ofwhich the signals from each transducer are picked oh the line oracquired and combined in substantially the same phase in a single signalpickup circuit for each desired directivity of the array of transducers.

Thus, for example, one signal pickup circuit comprises in seriesconnection the following secondary windings: coil 44' in line 33; coil$5 in line 34; coil 66 in line 35; coil 77 in line 36; and coii as inline 37. With this arrangement the received impulses in the individualtransducers 1G, 9, 8, 7 and 6 are successively retarded in time byamounts corresponding, respectively, to the electric delay distance fromthe beginning of each of the respective thereto connected delay lines tothe point therein where the picket secondary winding 4%, S5, 66, 77 or83 is situated. This is a condition for reception, with maximumintensity, of a sound approaching substantially in the direction of thearrow A since the sound wave will arrive at the forward transducers 6and 5 earlier than at the other transducers 7, 3, 9, it), 12, 3 and d,and therefore the delay will necessarily be progressively less for theother transducers than for the forward transducers 6 and 5, in the lineof reception of the sound waves.

It should be noted that the amount of compensation with respect toamplitude in this arrangement of transducers is not equal between ailtransducer units, the desired amplitude compensation or contributionbeing proportional approximately to a sine or cosine function. For thisreason, if a sound wave is approaching from the direction of the arrowA, the compensation between the successive units d, 9 and in, forexample, will necessarily have to be progressively greater than thatbetween the more forward units 6 and 7. The values of time delay persection of each delay line and the number of line sections between theinput end of the line and the pickofl secondary coil of a given signalcircuit for each transducer will determine the total delay of the signalfrom each transducer. For instance, a received signal from transducer 10is not delayed at all in line 33 as far as the first pickofi secondarycoil 44 is concerned. The corresponding received signal, however, fromthe next adjacent transducer 9 is delayed by two sections of line 34before it reaches the next pickofr" secondary coil 55' in the signalpickup circuit. The correspondingreceived signal from the nexttransducer 8 is delayed by four sections of its line 35 before itreaches the next pickofi secondary coil 66-. In asimilar manner, thereceived signal from the next transducer 7 is delayed by six sections ofline 36 before reaching the next pickofi secondary coil 77 while thereceived signal from the forwardmost transducer 6 is delayed by sevensections of line 37 before it reaches the next pickoff secondary coil88'.

Thus the signals that are acquired by the pickofi secondary windings 44,55', 66, 77, 88', connected in series, have each been delayed thecorrect amount to appear substantially simultaneously in the signalpickup circuit and provide overall reception with maximum intensityunits 6, 7, 8, 9 and 10. The complete signal pickup acquires signalenergy, by way of similar circuit arrangements aifording the samedelay-compensation scheme, from transducers 1 to 5, inclusive, also.These latter transducers, considered in the order 5 to l, inclusive, are

connected, respectively, to delay lines 38 to 42, inclusive.

For the sound wave arriving in the direction of the arrow A, theforwardmost transducer 5 has the same compensation as the correspondingtransducer 6. To this end, the free end of the last pickoil secondarywinding 88' of the portion of the signal pickup circuit described aboveis connected to pickoff secondary winding 98" of delay line 38, whichpicks off the received signal from the section of line 38 thatcorresponds to the section of line 37 from which said pickoif secondarywinding 88 acquires its received impulse signal. Following this signalpickup circuit through to completion, the remaining pickoif secondarywindings in the circuit are 107", 116", 125", and 134", in seriesconnection, the last winding 134 being grounded at its free end. Theconnection through ground returns to a parallel-resonance circuit 51 andtherethrough to the commutator switch 52, thus completing the seriessignal pickup circuit for all of the transducers 1 to 10, inclusive,which provides reception with maximum intensity of a signal arriving inthe direction of the arrow A.

The commutator switch 52 is provided with a contactor 52, whichcontactor shuold be in contact with the segment 53 of the switch 52 toconnect the above-described signal pickup circuit for use. In theposition illustrated in the drawing, however, the contactor 52' is incontact with another commutator segment 59 which is connected through awire 6% to the first pickotf secondary winding 64 of delay line 35. Thiswinding is at the beginning of the delay line 35, and to this delay linetransducer 8 is connected via wire 25. Thus, in the signal circuit thatis connected to segment 59, the least amount of delay, or compensation,is applied to the signal transducer 3. This complete signal circuitincludes, in series connection, the following pickoif secondarywindings: 64', 75', 86', 97', 108", 118", 127", 136", and then on tonext succeeding lines (not shown) which would include in successiveorder the received signal impulses from transducers 21 and which wouldhave successively reduced compensation as in the previous illustrationdescribed. In this latter signal circuit, the wave front to which thesystem responds, during reception, with maximum intensity is that whichis approaching and arrives in the direction of the arrow B.

The commutator switch contact 52' would be turned through the angle 6 inmoving from commutator segment 53 to segment 59. This angle 6 is alsothe angle between the two arrows A and B, shown in the drawing as theangle between the wave fronts arriving along the direction of thesearrows. Thus, the angle through which the commutator switch is rotatedcorresponds directly to the angular change in directivity of the transducer array, and the switch 52 can conveniently indicate directly thedirection of a received signal, or determine directly the direction of atransmitted signal. By continued movement of the commutator switchcontactor 52, the transducer assembly is electrically oriented indirectivity without physical movement of the transducers in any way.

The electronic commutator switch tube device of the above-referred-tocopending application may advantageously be employed as the switch 52,to provide rapid and smooth commutation and scanning. In such a tube thecontactor 52 is an electron beam, and the tube is provided with anaccelerating electrode, illustrated schematically in the drawing hereinas an electrode 76 provided with an accelerating potential by a batteryP. As explained in said copending application, a rotatable coil 69 maybe employed to sweep the electron beam from one commutator segment tothe next.

The system shown in the drawing can be employed both for transmissionand reception since the signal, if impressed upon a signal circuit, willbe delayed in the "delay lines similarly in transmission as in receptionso that energy transmitted by way of the transducers produces a planewave front at which front the compressional wave energy is all in thesame phase.

The system may be employed in any medium. The amount of delay employedto bring the signals from the individual transducers or radiators intothe same phase is dependent upon the transmission velocity of the wavesbeing employed in the medium, and upon the particular geometry of theconfiguration of transducers or radiators.

As will be appreciated, with this invention, scanning may easily be madeautomatic. For this purpose the receiving and indicating circuitcomprises an amplifier 60 and a cathode ray oscilloscope 61, the beam 62of which may be synchronously rotated by means of a control coil 63, orin any other suitable manner. The control coil 63 may be, for example,rotated synchronously with the beam sweeping coil 69 of commutatorswitch 52, under control of any convenient device functioning as a syn-ChlOIllZCl, for example, a common drive motor or a servo system. Thesignal appearing across the tuned circuit 51 is amplified by theamplifier 6t} and impressed upon the intensity control grid 74? of thecathode ray tube, which may be made positive by the incoming signal topermit the beam to produce an indication on the fluorescent face of thecathode ray tube. he system of the present invention in its preferredform employs a cathode ray oscilloscope, as indicated at 61, with acathode ray beam which is normally suppressed by the grid 70 except whena signal is received.

While the invention may be emplyed in any type of scanning or searchsystem, and for echo ranging and/ or direction finding purposes, theadvantages thereof are highly appreciated in echo ranging systemsemploying the time-of-travel method. In these systems, during each dutycycle the direction of maximum response of the transducer or radiatorarray may be rotated through. the entire 360 degrees of azimuth aboutthe searching station a great number of times, thereby presenting acomplete plan posit-ion indication for each transmitted energy pulse.

One of the features of the invention that makes a satisfactorypresentation possible is the employment of loss-less delay lines. Thesignals that are acquired or picked off from these lines are voltagesignals; substantially no current is drawn from any of the delay lines.The signal circuits are connected in series with the parallel resonantcircuit 51 for utilization. This circuit develops a very high impedancein series with the pick-oil secondary windings, preventing the flow ofany but the minutest currents through the signal circuits. It will berecalled that each delay line is terminated in its characteristicimpedance 43, so that all the lines are matched to the source and thereare no standing waves. The signal circuits do min not disturb thismatching, and-thereresults a practically loss-less network, able topresent a satisfactorily strong signal to the amplifier 60 at very highscanning rates.

The construction of the lens network is not complex. The delay lines mayemploy as signal output inductors-the primary windings of small andcompact prefabricated transformers having on one form the primary andtwo secondary windings. Such a prefabricated transformer easily providesthe type coupling between the'delay lines and the signal circuits thatis desirable.

The above arrangement of individual delay lines for each transducerunit, with a permanent arrangement of signal pickotf windings coupledwith and properly placed along each line, and arranged to providepermanent cir cuits corresponding, respectively, todefinite directionsof approach or recession of signals, may be termed a lens network, sincethe signal'pickup' circuits-coupled to the delay lines cause the arrayto act on the whole as a lens, to bring signals approaching from a givendirection and incident upon the individual transducers or radiatorsatdifierent times into the same phase or into a focus in that signalcircuit corresponding to the given direction. The arrangement actsanalogously to an optical lens which focuses parallel rays at a pointinthat the individual signals are brought into a single circuitsimultaneously; and, as in the optical case, the process is completelyreversible.

it will be noted in the present invention that the transducers are notrotated, but stationary, and'thatthe network of delay lines iselectrically oriented by means of the signal circuits, which are allalike. The signal circuits may be designed to avoid secondary'lobes bothin trans mitting and receiving. The wave pattern in this case may besuch as to enhance the output or sensitivity of the center units of thearray and diminish those at the edges. This is accomplished by havingmore coupling turns on the end-most pickoif secondary windings, such as88, 93, 98", 1%, 168", 118, 118", etc;, than on the other sections ofthe delay lines not so near the end. In fact, the energy output or inputmay increase progressively in the direction towards the free end of eachline.

It should be borne in mind that the invention can be employed in radarsystems, where the signal is acquired or radiated by means of antennaeor radiation, as well as in underwater sound systems, whereelectro-acoustic transducers are employed; that is, the array oftranducers 1 to 21, inclusive, maybe, if desired, an array ofradioantennae.

Having described my invention, I claim:

1. A system comprising, in combination, a group of wave energytransmitting or receiving elements spaced symmetrically in a fixed arrayfor transmitting or receiving in any desired direction, a lens networkhaving a separate delay line connected to each element of the group, agroup of similar. signal circuits each coupled with each of the delaylines at fixed selected points for picking ofi or impressing energy,each signal circuit corresponding respectively to given-directivity ofthe group, and a commutator-type selector switchhaving a movablecontactor and a plurality of commutator segments selectively engageablethereby, each of which segments is connected to one of said signalcircuits, for selecting a signal circuit corresponding to the desireddirectivity.

2. A system comprising, in combination, a group of wave energytransmitting or receiving elements spaced symmetrically in a fixed arrayfor.transmiittingiorvreceiving in any desired direction, a lens networkhaving individual delay lines connected to each element of the group, aplurality of electrical circuits each fixedly coupled similarly to aselected group of said delay lines for cophasing in each circuit thesignal energy from or to said elements corresponding to a predetermineddirectivity of said array, and an electronic commutator tube having acathode beam and a plurality of commutator segments,

6 a each of which is connected to. oneof said electrical circuits.

3. A system comprising, in combination, a group of wave energytransmitting or receiving elements spaced symmetrically in a fixed arrayfor transmitting or receiving in any desired direction, a lens networkhaving individual delay lines connected to each element of the group,- aplurality of electrical circuits each coupled to a prescribed portion ofeach one ofa selected group of said delay lines for cophasing in eachcircuit the signal energy from or to said elements corresponding to apredetermined directivity of said array, an electronic commutator tubehaving a cathode beam and a plurality of commutator segments, each ofwhich is connected to one of said electrical circuits, and meansoperative during receiving for indicating the directionofthe energy soreceived;

4. A system comprising, in combination, a: group of wave energytransmitting'or receiving elements spaced symmetrically in a fixedarrayfor transmitting or receiving in any desired direction, a lens networkhavin'gindividual delay lines-for retarding the wave applied to orpicked up at each element. of the group, a plurality of electricalcircuits each fixedly coupled to a prescribed portion of each one of aselected group of said delay lines for cophasing signal energy from orto said elements to provide directivity to said array, an electroniccommutator tube having a cathode beam and a plurality of commutatorsegments, each of which is connectedto one of said electrical circuits,a cathode ray oscilloscope for indicating the receipt of a wave energysignal and means for synchronizing the rotation of the cathode ray beamsin the oscilloscope and commutator tube for indicating the direction ofthe signal so received.

5. A system comprising, in combination, a group of wave energytransmitting andreceiving elements spaced symmetrically in a circle inafixed array, a plurality of similar delay lines permanently connectedone to each of said elements, a plurality of similar signal circuitseach fixedly coupled to all of said delay lines at prescribed points ofdelay corresponding to a particular directivity of'said group, acommutator switch having a movable contactor and a plurality ofcommutator seg ments selectively engageable thereby, each of whichsegments is connected to one of said signal circuits, and indicatingmeans for indicating the signal obtained in the switch-connected signalcircuit.

6. A system comprising, in combination, a group of wave energytransmitting and receiving elements spaced symmetrically in a circle ina fixed array, a plurality of similar delay lines permanently connectedone to each of said elements, a plurality of similar signal circuitseach fixedly coupled to all of said delay lines at prescribed points ofdelay corresponding to a particular directivity of said group, anelectronic commutator tube having a cathode beam serving as a connectinglink successively to each of said signal circuits, and indicating meansfor indicating the directivity of the signal obtained in the connectedsignal circuit.

7. A system comprising, in combination, a group of wave energy receivingelements spaced symmetrically in a circle in a fixed array, a pluralityof similar delay lines permanently connected one to each of saidelements, a plurality of similar signal circuits each fixedly coupled toall of said delay lines at prescribed points of'delay corresponding to aparticular directivity of said group, an electronic commutator tubehaving a cathode beam serving as a connecting link successively to eachof said signal circuits, a cathode ray oscilloscope having a cathode'beam, a grid control therefor, and means for rotating the beam about theoscilloscope screen, means connecting the commutator tube to saidcontrol grid for providing an indication on the oscilloscope by controlof the 8. A system comprising, in combination, a group of wave energytransmitting and receiving elements spaced symmetrically in a fixedarray for transmitting or receiving in any desired direction, anelectrical delay line permanently connected to each element, meansincluding a plurality of similar signal circuits permanently coupledeach to each of said delay lines in prescribed sections at variousdistances along the respective lines for transferring signal energy atsuch points of coupling for producing or detecting a signal wavecorresponding to a particular directivity, the coupling with sectionsfurther removed from the input ends of the lines providing progressivelya transfer of a greater amount of signal energy.

9. A system comprising, in combination, a group of wave energytransmitting or receiving elements spaced symmetrically in a fixed arrayfor transmitting or receiving in any desired direction, a separate delayline connected at one end to each element and terminated at the otherend in its characteristic impedance, a group of similar signal circuitseach fixedly magnetically coupled at selected points to each of thedelay lines for picking off or impressing wave energy, each signalcircuit corresponding to a given direction, and a commutator-typeselector switch having a movable contactor and a plurality of commutatorsegments selectively engageable thereby, each of which segments isconnected to one of said signal circuits, for selecting the desiredsignal circuit corresponding to the desired direction.

10. A system comprising, in combination, a group of wave energytransmitting or receiving elements spaced apart in a fixed array, eachadapted for transmitting or receiving in a plurality of directions, anindividual electrical delay line connected at one end to each elementand terminated at the other end in its characteristic impedance, and aplurality of permanently fixed signal circuits corresponding each to apredetermined directivity of said group, each circuit being permanentlycoupled to each delay line at the electrical point of delay appropriatefor the desired directivity of the group for that circuit, commutatorswitch means including movable contactor means and a plurality ofcommutator segments selectively engageable thereby, each of whichsegments is connected to one of said signal circuits, and signal meansconnected to said contactor means.

11. A system comprising, in combination, a group of wave energytransmitting or receiving elements spaced apart in a fixed array, eachadapted for transmitting or receiving in a plurality of directions, anindividual electrical delay line connected at one end to each elementand terminated at the other end in its characteristic impedance, and aplurality of permanently fixed signal circuits corresponding each to apredetermined directivity of said group, each circuit being permanentlycoupled to each delay line at the electrical point of delay appropriatefor the desired directivity of the group for that circuit, andelectrical commutator means having a movable contactor and a pluralityof commutator segments selectively engageable thereby, each of whichsegments is connected to one of said signal circuits, for selecting adesired signal circuit.

12. A system comprising, in combination, a group of wave energytransmitting or receiving elements spaced apant in a fixed array, eachadapted for transmitting or receiving in a plurality of directions, anindividual electrical delay line connected at one end to each elementand terminated at the other end in its characteristic impedance, and aplurality of permanently fixed signal circuits corresponding each to apredetermined directivity of said group, each circuit being permanentlycoupled to each delay line at the electrical point of delay appropriatefor the desired directivity of the group for that circuit, and meansproviding a substantially infinite impedance in series with each of saidsignal circuits during use thereof, whereby said delay lines aresubstantially undisturbed electrically by the opening and closing ofsignal circuits.

13. A system comprising, in combination, a group of wave energytransmitting or receiving elements spaced apart in a fixed array, eachadapted for transmitting or receiving in a plurality of directions, anindividual electrical delay line connected at one end to each elementand terminated at the other end in its characteristic impedance, and aplurality of permanently fixed signal circuits corresponding each to apredetermined directivity of said group, each circuit being permanentlycoupled to each delay line at the electrical point of delay appropriatefor the desired directivity of the group for that circuit, electricalcommutator means having a movable contactor and a plurality ofcommutator segments selectively engageable thereby, each of whichsegments is connected to one of said signal circuits, for selecting adesired signal circuit, and means connected in series with saidcontactor providing a substantially infinite impedance in series withthe selected signal circuit, whereby said delay lines are substantiallyundisturbed electrically during commutation.

14. A system comprising, in combination, a group of wave energytransmitting or receiving elements spaced apart in a fixed array, eachadapted for transmitting or receiving in a plurality of directions, anindividual electrical delay line connected at one end to each elementand terminated at the other end in its characteristic impedance, and aplurality of permanently fixed signal circuits corresponding each to apredetermined directivity of said group, each circuit being permanentlycoupled to each delay line at the electrical point of delay appropriatefor the desired directivity of the group for that circuit, and anelectronic commutator tube having a cathode beam and a plurality ofcommutator segments, each of which is connected to one of said signalcircuits.

15. A system comprising, in combination, a plurality of wave energytransducer elements arranged in a fixed array, a plurality of individualnetworks each permanently intercoupling said elements to provide maximumresponse to a plane wave arriving at said array in a particulardirection, and commutator switch means having a movable contactor and aplurality of commutator segments selectively engageable thereby, each ofwhich segments is connected to one of said networks, whereby to selectthe network corresponding to a desired direction.

References Cited in the file of this patent UNITED STATES PATENTS1,682,712 Pierce Aug. 28, 1928 1,901,342 Lamson Mar. 14, 1933 1,977,974Rudolph- Oct. 23, 1934 1,995,708 Fischer Mar. 26, 1935 2,224,677 HanscomDec. 10, 1940 2,406,340 Batchelder Aug. 27, 1946 2,433,332 Beniofi Dec.30, 1947 FOREIGN PATENTS 546,202 Great Britain Dec. 6, 1939

